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TROPICAL STORM ALBERTO DISCUSSION NUMBER 5
NATIONAL WEATHER SERVICE MIAMI FL
4 AM EST SAT AUG 05 2000
TROPICAL STORM ALBERTO HAS BECOME BETTER ORGANIZED DURING THE PAST 6
HOURS WITH A SMALL CDO FEATURE DEVELOPING OVER THE SYSTEM CENTER.
BASED ON THE CDO AND 0600Z SATELLITE INTENSITY ESTIMATES OF 50 KT
FROM TAFB AND SAB...THE INITIAL INTENSITY HAS BEEN INCREASED TO 55
KT. OUTFLOW HAS IMPROVED TO THE NORTH AND THE OVERALL CLOUD PATTERN
HAS BECOME MORE CIRCULAR.
INITIAL MOTION IS 285/13. THERE HAVE BEEN SOME MINOR FLUCTUATIONS IN
THE STORM MOTION THE PAST 6 TO 12 HOURS DUE TO RE-ORGANIZATION OF
THE CENTRAL DEEP CONVECTION. HOWEVER...WITH SUCH A STRONG
SUBTROPICAL RIDGE TO THE NORTH OF ALBERTO...A GENERAL WEST-NORTHWEST
OR WEST TRACK IS EXPECTED THROUGH THE PERIOD. THE 00Z UKMET RUN IS
SOMEWHAT CONFUSING WITH THE VORTEX TRACKER INDICATING A 72-HOUR
POSITION NEAR 18N 48W...WHILE THE SURFACE TO 850 MB FIELDS SHOW THE
CENTER OF ALBERTO CLOSER TO 15N 44W. WE LIKE THE OVERALL SYNOPTIC
PATTERN OF THE UKMET AND THE SPEED OF THE VORTEX TRACKER...BUT NOT
THE POSITIONS. THE PREVIOUS 2 MODEL OUTPUTS WERE CLOSER TO 16N 45W
AND WE HAVE FOLLOWED THAT TREND. THE GFDL HAS HAD A SHARP RIGHT OF
TRACK BIAS THE PAST 24 HOURS...SO I HAVE PLACED LITTLE FAITH IN THAT
MODEL. THE OFFICIAL TRACK IS SIMILAR TO THE PREVIOUS ONE AND BETWEEN
THE UKMET AND GFDN VORTEX TRACKER POSITIONS. WE HAVE ALSO MADE A
MORE WESTWARD BEND IN THE TRACK AFTER 48 HOURS BASED ON A POSSIBLE
200 MB CONFLUENT ZONE SETTING UP BETWEEN WEAK NORTHWEST TO WESTERLY
UPPER-LEVEL FLOW AHEAD OF A DEEPENING TROUGH AND THE POLEWARD
OUTFLOW OF ALBERTO...WHICH SHOULD ACT TO RE-INFORCE THE SUBTROPICAL
RIDGE AXIS TO THE NORTH OF THE SYSTEM.
NO SIGNIFICANT CHANGE TO PREVIOUS INTENSITY FORECAST OR PHILOSOPHY.
ALBERTO IS EXPECTED TO GRADUALLY MOVE OVER SLIGHTLY COOLER WATER
AFTER 12 HOURS. SINCE ALBERTO IS ALSO A RATHER SMALL TROPICAL
CYCLONE...SMALL CHANGES IN THE CENTRAL DEEP CONVECTION CAN RESULT IN
SIGNIFICANT SHORT TERM INTENSIFICATION. FROM 36 TO 48 HOURS...ALL
THE GLOBAL MODELS AGREE ON DIGGING A 200 MB TROUGH TO THE NORTHWEST
OF THE SYSTEM...WHICH SHOULD AID THE DEVELOPMENT OF THE POLEWARD
OUTFLOW AND ENHANCE THE INTENSIFICATION PROCESS.
FORECASTER STEWART
FORECAST POSITIONS AND MAX WINDS
INITIAL 05/0900Z 13.7N 28.7W 55 KTS
12HR VT 05/1800Z 14.2N 30.6W 65 KTS
24HR VT 06/0600Z 14.7N 33.4W 75 KTS
36HR VT 06/1800Z 15.1N 36.4W 80 KTS
48HR VT 07/0600Z 15.5N 40.0W 85 KTS
72HR VT 08/0600Z 16.0N 47.0W 85 KTS
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